An electric motor/generator generally includes a rotor assembly having a plurality of magnets of alternating polarity around the outer periphery of the rotor. The rotor is rotatable within a stator which generally includes a plurality of windings and magnetic poles of alternating polarity. In a generator mode, the rotation of the rotor causes the permanent magnets to pass by the stator poles and coils and thereby induce an electric current to flow in each of the coils. Alternately, if an electric current is passed through the stator coils, the energized coils will cause the rotor to rotate and thus the generator will perform as a motor. As with any energy conversion device, the motor/generators are less than 100 percent efficient, and reject some energy as heat. Efficient removal of this waste heat is desirable.